Hoffman W E, Lingamneni P, Minshall R, Miletich D J, Albrecht R F
Department of Anesthesiology, University of Illinois, Chicago.
Anesth Analg. 1993 Feb;76(2):274-8.
alpha 2-Adrenergic agonists decrease sympathetic activity and improve outcome from brain ischemia. We evaluated whether changes in alpha 2-adrenergic receptor binding activity may be important in the sympathetic depressant and cerebral protective effects of halothane (1.1% inspired) or isoflurane (1.4% inspired) compared to fentanyl/nitrous oxide (N2O) anesthesia. Brain alpha 2-adrenergic receptor binding was measured using [3H]-clonidine in each of four treatment conditions: 1, unanesthetized; 2, anesthetized (fentanyl/N2O, halothane, or isoflurane): 3, anesthetized with ischemia; 4, after 4 h recovery from ischemia. Ischemia was produced by right carotid artery ligation combined with hemorrhagic hypotension to 30 mm Hg for 30 min. Both halothane and isoflurane decreased alpha 2-adrenergic receptor density 20% compared to unanesthetized values (P < 0.01). This decrease was attenuated in ischemic tissue. There were no consistent changes in receptor affinity. These results suggest that inhaled anesthetics decrease the number of alpha 2-adrenergic receptors. This decrease appears to be unrelated to plasma catecholamine concentrations but may be influenced by the degree of ischemia.
α2 - 肾上腺素能激动剂可降低交感神经活性并改善脑缺血的预后。我们评估了与芬太尼/氧化亚氮（N2O）麻醉相比，氟烷（吸入浓度1.1%）或异氟烷（吸入浓度1.4%）的交感神经抑制和脑保护作用中，α2 - 肾上腺素能受体结合活性的变化是否重要。在以下四种治疗条件下，使用[3H] - 可乐定测量脑α2 - 肾上腺素能受体结合：1，未麻醉；2，麻醉（芬太尼/N2O、氟烷或异氟烷）；3，麻醉并伴有缺血；4，缺血后恢复4小时。通过右颈动脉结扎并将出血性低血压降至30 mmHg持续30分钟来产生缺血。与未麻醉值相比，氟烷和异氟烷均使α2 - 肾上腺素能受体密度降低20%（P < 0.01）。这种降低在缺血组织中减弱。受体亲和力没有一致的变化。这些结果表明吸入麻醉剂可减少α2 - 肾上腺素能受体的数量。这种减少似乎与血浆儿茶酚胺浓度无关，但可能受缺血程度的影响。
